The present invention relates to a portable handoperated lawn aerator and more particularly to a device for extracting a plug approximately three inches long and onehalf inch in diameter from a lawn.
There are several hand-operated lawn aerators now known in the art. Once such device is shown in U.S. Pat. No. 3,210,112 to Glynn. This patent shows a hollow tubular cutting head attached to an upwardly extending handle. When the cutting head is forced into the ground, a plug of earth and thatch is forced into the tubular cutting head. The handle is hollow and encloses a spring which resiliently acts on a plunger element. When the plunger is driven downwardly, the plunger element forces the plug of earth from the tubular cutting head. The spring and associated members are provided to bias the plunger in the upward direction. Once the plunger is extended to extract the plug from the tubular cutting head and the plunger released, the spring moves the plunger to its upward, normally-resting position. As shown in this patent, the plunger element has a small cross-sectional area relative to the inside cross-sectional area of the tubular cutting head. In wet soil the small cross-sectional plunger is generally not as effective in removing a plug of soil as a device which has a plunger element extending across the entire corss-sectional area of the inside open area of the tubular cutting head.
U.S. Pat. No. 4,585,072 to Martinez describes another gardening tool with a plug ejector. This patent also illustrates a tubular cutting head having a handle attached. The plunger element normally rests at the entrance to the cutting head cavity. When the device is shoved into the ground, the plunger is moved upwardly as it rides on the surface of the soil. A handle is attached by a rod element to the plunger. When the device is lifted away from the ground and this handle is forced downwardly, the plug is forced out of the tubular cutting head. This device uses no springs and the plunger rod element is not protected from mud, soil, or moisture.
U.S. Pat. No. 1,692,436 to Deane shows another cutting device having a tubular cutting member with a plunger and spring mechanism located in the tubular cutting member to assist in removing the plug from the cutting head. In this device, the spring is used to bias the plunger in a downward direction. The spring is compressed by the soil when the tubular cutting member is driven into the soil. The tubular cutting member as described is open at the top. In moist soil conditions, the cutting head is subjected to corrosion caused by mud, moisture and soil. In addition, since the cutting head is open at the top, such materials collect on the top side of the plunger which may cause corrosion and render the cutting device inoperable. The spring mechanism is located in an exposed position near the plunger and is also subjected to the corrosive influence of mud and moisture.
From the above, it is recognized that problems associated with known lawn aerators include the failure to protect the spring mechanism, plunger rod, and plunger from moisture and soil which can corrode these parts.